In Step 3A, VPA will be added to enfuvirtide for 16 weeks. The study will be discontinued for participants who do not respond. Study visits will occur at screening, entry, Day 0, and Weeks 1, 2, 4, 8, 12, 16, and 22. A physical exam and blood and urine collection will occur at all visits. Leukapheresis will occur after screening, at entry, Day 0 and Weeks 12 and 16.